Regenerator of acid reaction lubricant residues

ABSTRACT

The invention relates to a method for regenerating reaction lubricant residues containing acid organic lubricants refused and processed during cold forming and multivalent metal ions and phosphate ions, wherein said reaction lubricant residues undergo the following procedural steps: a) precipitating metal ions from the metal organic compounds by adding phosphoric acid and/or acid phosphoric acid esters; b) dissolving water-soluble impurities by adding water; c) separating the solids from the lubricant components and from the aqueous phases that are incompatible with the oily lubricant components, and whereby d) acid phosphoric acid esters for adjusting the free acid at a value of less than 10 points and for adjusting a total acidity point value of less than 70 is adjusted at a free acid. total acidity ratio having a value in the range of 0.15 to 0.5. The separation indicated in step c) preferably occurs by means of a centrifuge at 2,000 to 3,000 g, especially at 8,000 to 15,000 g.

DESCRIPTION

This Application is A 371 of PCT/EP98/06708 Filed on Oct. 22, 1998.

The invention relates to a method for the regeneration of acidic,organic lubricant stripped during the cold forming and processed, aswell as reaction lubricant residues containing multivalent metal ionsand phosphate ions.

Acidic reaction lubricants have an oily character and are distinguishedin that, in addition to an organic lubricant, they contain constituentswhich are capable of forming a conversion covering on the surface of theworkpiece to be transformed U.S. Pat. No. 3,525,651, U.S. Pat. No.2,739,915, DE-B-21 02 295, EP-A-24 062, EP-A-25 236). The reactionlubricants, which are in practice the most important by far, contain ascomponent which is capable of forming a conversion covering phosphoricacid polyvalent metal ions phosphate. In the treatment of the workpiecesto be deformed iron phosphate layers are essentially produced thepresence of phosphoric acid, of polyvalent metal phosphates beingproduced with the use of reaction lubricants containing polyvalent metalphosphates. The reaction lubricants usually applied when dippinggenerate on the surface of the workpiece a firmly intergrown conversioncovering which guarantees that during the deformation a high measure ofseparation of workpiece and deforming tool takes place, and that on theother hand, a secure binding of the organic lubricant to the workpiecesurface is given.

Cold forming happens most frequently with the use of reaction lubricantstakes place by means of slide-drawing. In this respect, the excessreaction lubricant is stripped off at the outer drawing matrix.

If the slide-drawing takes place with the use of a drawing mandral,excess reaction lubricant is discharged, in addition, from the pipeinterior to the outside. The reaction lubricant residues stripped inthis way are collected and usually disposed of as waste. A reuse of thestripped reaction lubricant residues is not possible because a changehas taken place, as a result of temperature strain and pressure load,such that its original property of layer formation has been completelylost. In addition, rubbed-off metal parts are produced as a result ofthe friction forces prevailing during the deforming procedure. These arepresent in undissolved form, but are also present in dissolved form asorganic and is inorganic iron compounds, as a result of reaction withfurther components of the reaction lubricant. The metallic iron contentin the reaction lubricant residue prevents its reuse as a result ofscratch formation on the pipes to be drawn. In addition, organic ironcompounds thicken the reaction lubricant in such a way that a dipping orcirculating process can no longer be carried out economically as aresult of high lubricant consumption.

The aforementioned disposal of the residues of reaction lubricantsusually takes place by burning. In this respect, however, not only arecombustion products produced, which can represent a considerable strainon the environment, but components of the reaction lubricant which arevaluable in themselves are destroyed.

The object of the present invention is to provide a method for theregeneration of acid reaction lubricant residues, stripped during thecold forming and processed, which allows the restoration of a functionalreaction lubricant with the simultaneous use of a substantial part ofthe components present in the reaction lubricant residues.

The object has been achieved by developing the method of theabove-indicated type in accordance with the invention in such a waythat, there is added to the reaction lubricant residues, which havepassed through the procedural steps of:

a) precipitating metal ions from organometallic compounds by addition ofphosphoric acid and/or acid phosphoric acid esters,

b) dissolving water-soluble impurities by the addition of water, and

c) separating the lubricant component from solids and from aqueousphases which are incompatible with the oily lubricant component,

d) acid phosphoric acid ester to adjust the free acid to a value of atleast 10 points and to adjust to a total acidity point number of atleast 70, with the adjustment of the ratio of free acid: total aciditybeing to a value in the range of 0.1 to 0.5.

According to the nature of the stripped reaction lubricant residues, itis advisable to add a filtration in order to remove coarse impurities.For this purpose, heating advantageously takes place before thefiltration, in order to reduce the viscosity of the reaction lubricantresidues.

After the treatment by the addition of phosphoric acid and/or acidphosphoric acid esters corresponding to procedural step a) and theaddition of water corresponding to procedural step b), a multi-phaseoily product is obtained, the individual phases of which contain thedifferent impurities partially together with the valuable substance tobe recovered.

In the subsequent procedural step c) the separation of the lubricantcomponent from solids and from aqueous phases incompatible with the oilylubricant component takes place with the aid of filters, decanters,separators, but preferably with the aid of centrifuges. In this respect,all solids and all phases incompatible with the oily phase, for examplethe aqueous or is aqueous-acid phase, and all phases, the density ofwhich lies above that of the organic lubricant originally used, areseparated.

According to a preferred development of the invention the separationcorresponding to step c) takes place by means of a centrifuge at 2000 to30000 g. The use of a centrifuge at 8000 to 15000 g is particularlyadvantageous.

As a result of the separating process, an oily substance is obtained,which contains substantially all organic components of the originalreaction lubricant. However, there is a deficiency of the componentsresponsible for the formation of the conversion covering because, as aresult of reaction during the drawing procedure, a considerable part ofthe reactive component of the reaction lubricant has been broken down.To restore the functional reaction lubricant acid phosphoric acid estersare added to the oily lubricant component, obtained after passingthrough step c), to adjust the free acid to a value of at least 10points and to adjust the total acidity point number to at least 70. Inthis respect, it is to be observed that the ratio of free acid: totalacidity is adjusted to a value in the range of 0.1 to 0.5. If necessary,it can be advantageous additionally to add phosphoric acid in order toadjust the free acid.

Acid esters of saturated or unsaturated fatty alcohols, preferably witha chain length of 16 to 22 C atoms, are particularly suitable asphosphoric acid esters.

The adjustment of free acid and total acidity takes place according tothe following method of determination.

For the titration of the free acid about 1 g of the reaction lubricantis weighed exactly into a 300 ml Erlenmeyer flask. 60 ml xylene is addedto dissolve the lubricant. This solution is shaken in a 250 ml shakingfunnel a total of four times with a mixture of 10 ml demineralized waterand 20 ml ethanol. The separated ethanol/water phases are put into a 300ml Erlenmeyer flask and about 2 ml of an indicator solution, consistingof 0.1% by weight bromocresol green and 99.9% by weight ethanol, areadded.

Thereafter, the titration takes place with 0.1 m alcoholic potassiumhydroxide solution until there is change in colour from green to blue.The free acid content is given as

consumption (ml) potassium hydroxide solution×5.6 initial weight (g).

For the titration of the total acid content, about 1 g of the reactionlubricant is likewise weighed exactly into a 300 ml Erlenmeyer flask and100 ml of a solvent mixture, consisting of 0.1% by weight alkali blue(indicator), 42.9% by weight xylene, 28.5% by weight ethanol and 28.5%by weight isopropanol, are added. After complete dissolution of thelubricant the titration takes place with 0.1 m alcoholic potassiumhydroxide solution until there is change in colour from blue tored-purple. The calculation of the total acid is given by:

consumption (ml) potassium hydroxide solution×5.6 initial weight (g).

By suitable selection of the acid phosphoric acid ester and/or the fattyacid, the viscosity of the recovered reaction lubricant should liebetween 8 and 1000 mm²/sec at 60° C. The preferred range for reactionlubricants to be used in the dipping method lies between 8 and 100mm²/sec, for circulating products, the preferred range is 50 to 500mm²/sec.

EXAMPLE

At preparation for the slide-drawing, bright annealed steel pipes weretreated with a commercial reaction lubricant which contained

53% by weight mineral oil of viscosity 8 mPa sec (at 40° C.)

20% by weight oleic acid

15% by weight oleyl alcohol

5% by weight oleylamine

5% by weight polyphosphoric acid

2% by weight demineralized water

and had a content of free acid of 22 points and had a total acidity of98 points. The treatment took place by dipping at a bath temperature of65° C. for a duration of 10 min.

During the slide-drawing, which provided a cross section reduction of40%, residues of the reaction lubricant were stripped from the outer andfrom the inner surface of the workpieces, which residues had losteffectiveness as a result of chemical reaction between components of thereaction lubricant and the substrate surface during the dippingtreatment, but also as a result of the pressure load and temperaturestrain during the deforming procedure. The stripped reaction lubricanthad a total point number of 57, a free acid point number of 8, wasthickened and as such could no longer be used.

The preparation of the processed reaction lubricant for regenerationtook place in such a way that first of all it was collected in barrels,heated to 60° C. and thereafter was poured by way of a filter with apore diameter of 200 μm into a heatable agitator vessel.

Corresponding to procedural step a), 2% by weight of phosphoric acidwere added to the residues of the reaction lubricant located in theagitator vessel and the resulting mixture was stirred for 1.5 hours at atemperature of 50 to 65° C. in order to precipitate out the iron fromthe organometallic compounds. Thereafter, 3% by weight of demineralizedwater were added, corresponding to procedural step b), followed byfurther agitation at 50 to 65° C. for the duration of 1.5 hours in orderto extract water-soluble impurities. Subsequently, the separation of thesolid phase, primarily iron phosphate, and of the aqueous liquid phasetook place in a centrifuge which operated at an acceleration of 10000 g.The centrifuge discharge in this way was then homogenized in an agitatorcontainer. The product had a total acidity point number of 43 and a freeacid point number of 5. After the reaction lubricant residues had passedthrough the procedural steps a), b) and c), 17% by weight of an acidphosphoric acid ester of oleyl alcohol were added for the finalregeneration. In this way, a reaction lubricant regenerated material isobtained which had a total acidity point number of 98 and a free acidpoint number of 27.

The regenerated material obtained in the manner described above can beused, after adjustment of the water content to 2% by weight, both forsupplementing existing reaction lubricant baths and for providing newones.

What is claimed is:
 1. A method for the regeneration of acidic, organic lubricant stripped during a cold forming process from reaction lubricant residues containing polyvalent metal ions and phosphate ions, said method comprising passing said residues through the following steps: a) adding to said residues a component selected from phosphoric acid, phosphoric acid esters, and both phosphoric acid and phosphoric acid esters, to said residue to precipitate metal cations; b) adding water to dissolve water-soluble impurities; c) separating a lubricant component from said solid and aqueous phases, which phases are incompatible with said lubricant component; and d) adding acidic phosphoric acid ester to the remaining lubricant phase to adjust the free acid to a value of at least 10 points and to adjust total acidity point number to at least 70, with the adjustment of the ratio of free acid to total acidity being in the range of 0.1 to 0.5.
 2. The method of claim 1, wherein the separation in step c) is accomplished by centrifugation at 2,000 to 30,000 g.
 3. The method of claim 2, wherein said centrifugation is conducted from 8,000 to 15,000 g.
 4. The method according to claim 1, wherein additional phosphoric acid is added to adjust the free acid. 